Anchor bolt having elastically connected wedge members



Sept. 15, 1959 s. H. STRAND 2,903,933

ANCHOR BOLT HAVING ELASTICALLY CONNECTED WEDGE MEMBERS Filed Jan. 2 19572 Sheets-Sheet 1 FIG.1 FIG? n, a l; i: 8 i 7 l' ":Hi

1| {I I: 1} TI :l :1 L 44 INV TOR. Ann/Z 7 M 12,4, z/AWJ Sept; 15, 1959s. H. STRAND 2,903,938

' ANCHOR BOLT HAVING ELASTICALLY CONNECTED WEDGE MEMBERS Filed Jan; 2,1957 2 Sheets-Sheet 2 'FIG.4

IN V EN TOR.

ANCHOR BOLT HAVING ELASTICALLY CON- NECTED WEDGE MEMBERS Sven HugoStrand, Stockholm, Sweden Application January 2, 1957, Serial No.632,036

Claims priority, application Sweden January 18, 1956 4 Claims. (Cl. 85-2.4)

The present invention relates to a bolt to be anchored to the rock inthe ceiling and walls of galleries and rock chambers, which bolt is tobe inserted in a bored hole and secured there, so that for example acracky rock portion is held together, the free end of the bolt beingprovided with a nut and a washer or the like, and the invention issubstantially characterized in that two cooperpating wedges axiallydisplaceable in relation to each other rest against the end to besecured of the bolt and, coaxially in relation to the said bolt, one ofthe said wedges being fixed on the bolt, the second wedge being soarranged that one side thereof, by the action of an elastic member, iscaused to rest against the wall of the bore hole, while the other sideis caused to rest against the fixed wedge.

Different kinds of bolts to be anchored to the rock are already known,which are firmly anchored, whereby the ceiling and the walls ofgalleries and rock chambers will form the essential constituents of thebearing structure so that softer or cracked rock portions are preventedfrom falling down. For this purpose there is a substantial number ofdifferent embodiments of bolts, for example cotter bolts, expansionbolts, et cetera, which for the attachment to the rock are threaded.Such bolts are also known the upper part of which has cut-out cones.

instead of threads. When dimensioning cotter bolts the slotting in thebolt must be greatly considered, as the said slot weakens the bolt morethan a thread. What is common to most of the earlier known bolts is thatthey are complicated and expensive to produce.

An advantage of a bolt according to the invention is that it can be cutto a suitable length on the working site due to the fact that it isthreaded in one end only.

The object of the invention is to provide a rock bolt which is eflicientand at the same time simple and cheap to manufacture.

The rock bolt according to the invention will now be described in detailwith reference to the accompanying drawings in which differentembodiments are shown. Fig. 1 shows a rock bolt just inserted in a boredhole and Fig. 2 shows the same rock bolt seen from the left in Fig. 1.Fig. 3 shows the rock bolt seen from above. Fig. 4 shows anotherembodiment of the invention and Fig. 5 shows the same embodiment seenfrom above. Fig. 6 shows a detail of the embodiment of Fig. 4 on alarger scale.

The rock bolt according to the invention consists of a cylindrical bolt1, which at its lower free end is provided with threads 3 for a nut 2.An arcuate wedge 4 is pressed to the upper end of the bolt 1 or appliedin some other manner. The concaveside of the wedge 4 that faces the boltis formed in such a manner that it rests against the bolt 1 along thewhole of its length and it is attached to the said bolt thereby that thelimit surfaces 5 and 6 pass beyond the central line of the bolt, so thatthe Wedge 4, when applied on the bolt 1, is clamped to the latter. Theconcave side of the wedge 4 that faces the bolt is provided withbarb-like teeth 7,

ited States Patent 9 a longitudinally towards each other.

2,903,938 Patented Sept. 15, 1959 "ice the edges 8 of which are at rightangles to the bolt and obliquely upwards. Due to the fact that theradius of the wedge 4 is somewhat smaller than half the diameter of thebolt 1, and due to the fact that the material from which the wedge 4 ismade is somewhat harder than the material of the bolt, the teeth 7 willcome into mesh with the bolt 1 when the wedge 4 is clamped thereto, anddue to the fact that the edges 3 are directed obliquely upward, the boltcannot be displaced, when pulled downward. The outer convex side of thewedge 4 that is the side remote from the bolt 1 is rounded in accordancewith the bolt and is tapered longitudinally and against the outer convextapered side of said wedge 4 another arcuate wedge 9 cooperatingtherewith tests,

the inner concave side of which is shaped complementary to the taperedconvex portion of the outwardly directed side of the wedge 4. The loosewedge 9 has at that side that is remote from the fixed Wedge 4 barb-liketeeth 10 disposed at right angles to the bolt 1, the edges 11 of thesaid teeth being directed obliquely downward, so that they engage thewall of a bore hole 12, when the bolt 1 is pulled downwards.

The two Wedges 4 and 9 are axially displaceable between themselves, anelastic member 13, comprising an endless rubber band or like readilyrupturable member encircling and drawing the two wedges together and Thecircumference of the endless rubber band 13 is so dimensioned that, whenthe bolt 1 is not inserted in a bore hole, the 'two wedges are locatedopposite each other. The rubber band 13 is fixed to the rock bolt in thefollowing way: Before the wedge 4 is fixed to the bolt 1, the rubberband 13 is threaded thereon along its longitudinal direction, wherebythat part of the rubber band 13 that is at that side of the wedge 4 thatfaces the bolt 1 is received in a slot 14 in the wedge 4. Thereafter thewedge 4 is pressed into its position on the bolt 1, and the loose wedge9 is inserted between the rubber band 13 and the wedge 4, the saidrubber band 13 being received in a recess 15 provided in the lower endof the wedge 9 and adapted to fix the wedges mutually.

Then the rock bolt is ready for use and it is inserted in a bore hole bymoving the wedge 9 somewhat downward so that it does not prevent theinsertion. The rock bolt is moved to the bottom of the bore hole 12, andwhen the bolt 1 is pulled, the edges 11 of the teeth 10 of the loosewedge will engage the wall of the bore hole, whereby the two wedges 4and 9 more and more will be placed opposite each other to an extentwhich is dependent on the size of the bore hole 12. The rubber band 13which then has no function to fulfill, will then be pressed to piecesbetween the Wedge 9 and the wall of the bore hole 12.

An essential advantage of the device according to the invention is thatthe forces acting upon the wedges will be substantially radiallydirected due to the fact that the surfaces facing each other of thewedges 4 and 9 are shaped in accordance with the bolt 1.

Another advantage is that, if the bolt is to be removed from the borehole after having been used for some time, this is very simple, and iscarried out in such a manner that, after the nut 2 has been loosenedfrom or removed from the bolt, the latter is moved longitudinally bystrokes from below, whereby the wedges 4 and 9 are loosened from eachother. When the bore hole is vertical, the wedge 9 will fall down andthe rod can be drawn out.

In the embodiment according to Figs. 4-6 the two wedges 4 and 9 are alsodisplaceable between themselves and are held together by a rubber strip16. One end of the said strip is fixed to a projection 19 on the upperedge of the fixed wedge 4, the other end being fixed to a projection 20on the lower edge of the loose wedge 9. Between the projections 19 and20 the rubber strip runs in a groove 17 provided in the outwardly facingside of the wedge 4. The loose wedge 9 has at the side facing the fixedwedge 4 a list '18 which engages the groove 17 in such a manner that,when the loose wedge 9 is displaced relatively to the fixed wedge 4 whenthe bolt 1 is fastened in the bore hole 12, the rubber strip will bepressed to pieces by the list 18.

Through cooperation between the list 18 in the loose wedge 9 and thegroove 17 in the fixed wedge 4, the wedges areprevented from being movedrelatively to each other, when the bolt is inserted in the bore hole.

The free end of the projection 20 of the loose wedge 9 is wider than theend fixed to the wedge 9, whereby the said projection can be attached toa thread for drawing out the wedge when the bolt is insertedhorizontally or slopingly.

As to bolts made in accordance with the embodiment shown in Figs. 4-6and which are inserted in horizontal or slightly sloping bore holes athread is attached to the projection 20 of the loose wedge 9 before thebolt is inserted, this being the reason why the free end of theprojection is wider. This thread which is to be so long that, when thebolt has been inserted, it protrudes out of the bore hole, can be ofnylon, iron or the like. When taking out a bolt applied in this mannerthe wedges are taken apart as per the above, whereafter the outer loosewedge 9 is drawn out by means of the thread.

Of course different embodiments Within the scope of the claims mayoccur. For example if one wishes that the bolt shall be more centered inthe bore hole, two fixed wedges may be applied on the bolt, one wedgebeing provided with ears, which engage corresponding indentations in theother wedge, so that the axially extending limit surfaces of the twowedges can pass the centre line of the bolt.

The bolt according to the present invention has been described inconnection with rock anchoring, but can of course be used in a pluralityof other fields, for example in concrete constructions, stone slabs andthe like, and also in wood constructions.

What I claim is:

1. In a bolt structure adapted to be anchored in a bore hole establishedin rock forming the ceiling or walls of galleries and rock chambers tohold a cracked rock portion together the combination comprising, a roundbolt shank adapted to be inserted in the bore hole, said shank being ofuniform diameter along at least a portion of its length and having athreaded end portion adapted to extend out of the bore hole forreceiving a washer and tightening nut, a first arcuate wedge memberextending longitudinally of and secured to the uniformly diameteredportion of said bolt shank at one side thereof, said wedge memberincluding a concave inner surface having a configuration complementaryto and resting throughout its length against the surface of saiduniformly diametered portion of said bolt shank and an outer convexsurface tapering longitudinally, a second arcuate Wedge member disposedat the same side of said bolt shank as is said first wedge member, saidsecond Wedge member having a concave and longitudinally tapered innersurface complementary to and engaging the outer convex tapered surfaceof said first wedge member and an outer convex surface extendinggenerally parallel with the axis of the bolt shank, said second wedgemember being slidable longitudinally of said first wedge member therebyto cause the outer surface of said second wedge member to bear againstthe adjacent side of the bore hole and the side of said bolt shankopposite said wedge members to bear against the other side of the borehole, and a readily rupturable endless elastic band extendinglongitudinally of and around the ends of said wedge members and undertension for drawing said wedge members toward each other, said elasticband being ruptured upon tightening of said bolt in the bore hole.

2. A bolt as defined in claim 1 wherein one flight of said endlesselastic band is located in a groove extending longitudinally in theconcave inner surface of said first wedge member, the other flight ofsaid elastic band extending longitudinally along the convex outersurface of said second wedge member and adapted to be crushed andruptured upon tightening of said bolt in the bore hole.

3. In a bolt structure adapted to be anchored in a bore hole establishedin rock forming the ceiling or walls of galleries and rock chambers tohold a cracked rock portion together the combination comprising, a roundbolt shank adapted to be inserted in the bore hole, said shank being ofuniform diameter along at least a portion of its length and having athreaded end portion adapted to extend out of the bore hole forreceiving a washer and tightening nut, a first arcuate wedge memberextending longitudinally of and secured to the uniformly diameteredportion of said bolt shank at one side thereof, said wedge memberincluding a concave inner surface having a configuration complementaryto and resting throughout its length against the surface of saiduniformly diametered portion of said bolt shank and an outer convexsurface tapering longitudinally, a second arcuate wedge member disposedat the same side of said bolt shank as is said first wedge member, saidsecond wedge member having a concave and longitudinally tapered innersurface complementary to and engaging the outer convex tapered surfaceof said first wedge member and an outer convex surface extendinggenerally parallel with the axis of the bolt shank, said second wedgemember being slidable longitudinally of said first wedge member, therebyto cause the outer surface of said second wedge member to bear againstthe adjacent side of the bore hole and the side of said bolt shankopposite said wedge members to bear against the other side of the borehole, and a readily rupturable elastic strip having one end thereofsecured to one end of said first wedge member and the other end securedto the opposite end of said second wedge member, said elastic stripextending longitudinally of said wedge member in a groove provided inthe convex outer surface of said first wedge member, and said secondwedge member being provided with a complementary list at the concaveinner surface thereof and between which groove and list said elasticstrip will be crushed and ruptured upon tightening of said bolt in thebore [hole 4. A bolt as defined in claim 3 wherein the end of saidsecond wedge member to which the end of said elastic strip is securedincludes means for attaching a thread enabling said second wedge memberto be withdrawn from a horizontal or slightly inclined bore hole uponloosening of said bolt.

References Cited in the file of this patent UNITED STATES PATENTS741,563 Stevens Oct. 13, 1903 798,440 McNulty Aug. 29, 1905 1,041,953Bennett Oct. 22, 1912 1,521,025 Hubener Dec. 30, 1924 1,585,532 Cole May18, 1926 1,964,427 Chandler June 26, 1934 2,004,264 Wyrick June 11, 19352,666,966 Lockett Jan. 26, 1954 2,878,668 Starling Mar. 24, 1959

